The present invention relates to methods for encapsulating leadframe items which each have a leadframe and an IC wired to it. The invention further relates to leadframe encapsulation systems employing the methods.
Increasingly, plastics materials such as epoxy-moulding compounds (EMC) are used for encapsulating leadframe items to form IC packages. The leadframe item is located in a mold, a pellet of plastics material is provided for the mold and the plastics material is molded around the leadframe item, in particular such that the mires become encased in the plastic material.
The use of EMC and the trend towards environmentally friendly compound formulation has given rise to increased levels of pellet dust, leading to various problems including increased mold flash after the encapsulation and disadvantageous movement of the wires (xe2x80x9cleadsxe2x80x9d).
The present invention aims to provide a new and useful method for encapsulating leadframe items.
The invention further aims to provide a new and useful system for encapsulating leadframe items.
In general terms, the present invention proposes that dust of the plastics material is removed from the encapsulation system, and in particular from those items where dust principally accumulates and/or where dust is most disadvantageous. The dust is typically brushed off, or transported out of the system by an air flow, e.g. to a filter.
Typically, these items are the dispenser which dispenses plastics material pellets into the mold, the holder which holds pellets before they enter the dispenser, the conveyor which transports the leadframe items into the molding region, and the molds themselves.
Furthermore, to reduce the level of dust which enters the molding region, the present invention proposes that the path along which the leadframe items are conveyed to the molding region is closed at times when it is not required to convey leadframe items to the molding region.
Furthermore, the present invention proposes that leadframe items are conveyed to the molding region under a cover including a pressure source, so that the dust is continually sucked (or in some embodiments blown) away from the leadframe items.
The invention may be expressed as methods for encapsulating leadframe items which include the above cleaning concepts. Alternatively, the invention can be expressed as a leadframe encapsulation system which employs the methods.